<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title></title>
</head>

<body>
<form id="myform"  method="post" action="#">
    <select name="grade1" id="grade1">
        <option value="1">初级</option>
        <option value="2">中级</option>
        <option value="3">高级</option>
    </select><br><br>
    <select name="grade2" id="grade2"></select>
</form>
<script>


var form = document.getElementById("myform");
var grade1 = form.elements["grade1"];                       
var grade2 = form.elements["grade2"]; 
grade1.onchange = function(){
	grade2.appendChild(grade1.options[grade1.selectedIndex]);
}
                
</script>
</body>
</html>
